The subject matter disclosed herein relates to grain boundary engineering and, more specifically, to using a laser or electron beam additive process to manufacture metal components with coincidence site lattice grain boundaries and/or low angle grain boundaries that improve resistance to stress corrosion cracking and intergranular corrosion.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Microscopically, polycrystalline metallic alloys are made up of individual crystallites commonly referred to as grains. These grains are connected together via grain boundaries. Grain boundaries are generally formed through recrystallization and grain growth process during metal part fabrication and heat treatment. After the metal process, most grains were connected through highly misoriented and equiaxed grain boundaries. Such grain boundaries can influence the mechanical properties of the metal, such as high and low cycle fatigue lives, yield strength, and/or creep. However, equiaxed random grain boundaries can be susceptible to stress corrosion cracking, which may be undesirable in certain application environments, such as oil and gas, nuclear, power generation, health care devices in the human body, and/or aircraft engines.
There are other types of grain boundaries, such as coincidence site lattice (CSL) grain boundaries and low angle grain boundaries, that exhibit improved properties as compared to equiaxed grain boundaries. CSL grain boundaries may refer to grain boundaries that are less than Σ29, and low angle grain boundaries may refer to grain boundaries between 1° and 5°. The improved properties exhibited by the CSL grain boundaries and low angle grain boundaries may include increased resistance to stress corrosion cracking by inhibiting intergranular cracking due to a disrupted network of the grain boundaries, increased hold time fatigue, and the like.
Grain boundary engineering may be performed in attempt to create CSL grain boundaries and/or low angle grain boundaries. Grain boundary engineering generally refers to techniques related to processing, evaluating, and classifying grain boundaries. Manipulation and optimization of grain boundaries in polycrystalline materials may be performed using grain boundary engineering. It is now recognized that improved grain boundary engineering techniques are desirable.